I have a 99 SEL with about 91k miles on it. Recently I have experienced big power loss on it when the engine is under load (uphill, etc.). But it surges - one second it loses power, and the next second it picks up and performs like normal. I thought it might be the o2 sensor, so I took it to Autozone to have the codes checked, but there were none. It has new fuel filter, air filter, and spark plugs but the problem continues. Anyone have any ideas? Thanks.
Scott

 

Partially working knock sensor maybe? Worth looking into anyway. There is info on this in the faqs.

*edit* Read this, this guy's problem seems to be pretty similar and people are telling him it's bad ignition coils. So this could be it especially since you have a '99 which commonly have bad coils.

 

I bet it's an O2 sensor.

A lazy O2 may not set a code but will effect performance.

What kind of plugs are you using? The VQ loves NGK plugs and make sure they are gapped correctly.

 

Its ignition coils I'll bet. I had surges too. Good luck.

 

Thanks guys. What's the best way to check the coils? I think it is in the Haynes manual, but mine seems to have disappeared. Since my problem seems to be somewhat intermitten I don't know if there will be a good way to check. Any ideas? Thanks.
Scott

 

The best way to test which coil is bad is to take them all out, go to your friendly local Nissan stealership, and individually cram them down a Nissan dealer's throat of your choosing. Whichever one comes back up is bad. Yes, that would mean they are all bad....

Barring this method however (and it has appeal to me since it was Nissan who screwed us in the first place), you can do a few things. Number one, some say to have the car running then disconnect a coil of your choice and see if it makes the car run worse. If it does, it is a good coil. I say this method doesn't work unless you are so far gone that one ignition coil isn't actually working at all - in which case you would likely have a CEL.

Second method involves a voltohmeter, the resistance in ohms should be about 12 - 15 I think. This again does not always highlight a bad coil, but some say they've found them this way.

Other method could be to take out each coil (without the car running this time) and examine the tops of them for signs of heat stress. This will barely be noticable, but can be seen as a slightly duller discolouration than the rest of the black colour. IMO, this is perhaps the most effective way, coupled with the voltohmeter. Heat stress is bad.

Last method. Replace all coils with new ones and heartily curse corporate Nissan for not owning up to their mistakes. If you have a 99, you will in all likelihood end up replacing them all anyways at some point in time. I'm currently on coil number 3 and I'm considering just biting the bullet and replacing the remaining ones.

Helpful?

 

check out my post in this thread i am having similar issues. http://forums.maxima.org/showthread.php?t=315658

 

Yeah Zack, I checked out your post. Somebody suggested checking the plugs to determine which cylinder was misfiring. I did that when I changed my plugs, but they all looked ok. No big difference in any of them. That may be because mine doesn't misfire constantly, but I don't know. I'm going to check the resistance to see if there's any difference there, but other than that I've got one more idea. I can buy one of each coil (front bank and rear) and swap them one at a time to see if it gets any better. It looks like eventually they may all go bad, but I'm not willing to replace them all at once right now.